Enanta Pharmaceuticals (ENTA) Study Result summary

Study design and population

• Phase IIb, randomized, double-blind, placebo-controlled study in 186 high-risk, non-hospitalized adults with acute RSV infection, including those with CHF, COPD, asthma, or age ≥75.

• High-risk criteria included age ≥65, chronic heart or lung disease; HR3 subgroup defined as CHF, COPD, or age ≥75, comprising 80–81% of the efficacy population.

• Patients randomized to 800 mg zelicapavir or placebo daily for 5 days, enrolled within 72 hours of symptom onset, with follow-up through day 28–33.

• Baseline characteristics and demographics were balanced between groups; most enrolled within 48 hours of symptom onset.

• Most patients had not received RSV vaccination; mean baseline symptom scores and viral loads were similar across groups.

Efficacy and clinical outcomes

• Zelicapavir led to faster complete symptom resolution by RIIQ and PGI-S, with up to one week improvement in HR3 patients (19 to 12 days, 35% improvement).

• Statistically significant 2-day faster symptom resolution by PGI-S in both overall and HR3 populations (p ≈ 0.045).

• No effect observed on time to mild LRTD symptoms for the primary endpoint in the overall efficacy population.

• Statistically significant improvement in RSV-13 symptom score at days 9 and 13–14 in HR3 population.

• Lower hospitalization rate: 1.7% with zelicapavir vs 5% with placebo; RSV-related hospitalizations 0–0.9% vs 5%.

Virology and antiviral effect

• Zelicapavir produced a 0.6–0.7 log drop in viral load at end of treatment.

• Statistically significant greater proportion of patients with undetectable viral load at end of treatment: 23.5% vs 10.0% (p = 0.0198).

• Median time to undetectable viral load was 4 days (overall) and 5 days (HR3) faster with zelicapavir.